58 THE LIFE-STORY OF INSECTS [CH. 



normal mandibulate type adapted for eating solid 

 food, the larval mouth is constricted and the slender 

 mandibles are grooved for the transmission of liquid 

 food. 



Turning to cruciform types of larva, we find the 

 caterpillar (fig. 1 b, c, d) distinguished by its elongate, 

 usually cylindrical body with feeble cuticle, short 

 thoracic legs and a variable number of pairs of 

 abdominal pro-legs, universal among the moths and 

 butterflies forming the great order Lepidoptera, and 

 usual among the saw-flies, which belong to the Hyme- 

 noptera. The vast majority of caterpillars feed on 

 the leaves of plants and their long worm-like bodies 

 with the series of paired pro-legs, are excellently 

 adapted for their habit of clinging to twigs, and 

 crawling along shoots or the edges of leaves as they 

 go in search of food. Of great importance to a cater- 

 pillar is its power of spinning silk, consisting of fine 

 threads solidified from the secretion of specially 

 modified salivary glands whose ducts open in the 

 insect's mouth at the tip of the tubular tongue which 

 forms a spinneret. 



On the same bush caterpillars of moths and of 

 saw-flies may often be seen feeding together. The 

 lepidopterous caterpillar, in our countries at least, 

 has never more than five pairs of pro-legs, situated 

 on the third, fourth, fifth, sixth, and tenth abdominal 

 segments; each of these pro-legs bears a number of 



